Latest scientists’ discovery – human-like footprints in the Greek island of Crete intrigues all mankind. It may put the established human evolution to the test. Footprints are approximately 5.7 million years old and were made at a time when previous research puts our ancestors in Africa – with ape-like feet.
Gerard Gierlinski, a paleontologist at the Polish Geological Institute specialized in footprints and the first author of the study, discovered the footprints by chance while he was on holiday on Crete in 2002. He identified the footprints as mammal but did not do any further interpretation of them at the time. Eight years later, in 2010 he returned to the site together with Grzegorz Niedzwiedzki, a Polish paleontologist (now at Uppsala University) and the second author of the study, to study the footprints meticulously. The conclusion the have come to was that the footprints were made by hominins.
Ever since the fossils of Australopithecus were discovered in South and East Africa during the middle years of the 20th century, it was believed that the origin of the human ancestry is in Africa. More recent fossil discoveries in the same region, including the iconic 3.7 million year old Laetoli footprints from Tanzania which show human-like feet and upright locomotion, have cemented the idea that hominins (early members of the human ancestry) not only originated in Africa but remained isolated there for several million years before dispersing to Europe and Asia. The latest discovery of approximately 5.7 million year old human-like footprints from Crete, published by an international team of researchers, overthrows this simple picture and suggests a more complex reality.
Human feet have a very distinctive shape which is different from all other land animals – long sole, five short forward-pointing toes without claws, and a hallux (‘big toe’) that is larger than the other toes, is unique. The feet of the great apes, our closest relatives, look more like a human hand with a thumb-like hallux that sticks out to the side. The Laetoli footprints, thought to have been made by Australopithecus, are quite similar to those of modern humans except that the heel is narrower and the sole lacks a proper arch. By contrast, the 4.4 million year old Ardipithecus ramidus from Ethiopia, the oldest hominin known from reasonably complete fossils, has an ape-like foot. The researchers who described Ardipithecus argued that it is a direct ancestor of later hominins, implying that a human-like foot had not yet evolved at that time.
Last author of the study, Professor Per Ahlberg at Uppsala University, says: ‘What makes this controversial is the age and location of the prints.’
The new footprints, found in Trachilos in western Crete, have distinctly human-like form. Especially the toes – the big toe is similar to our own in shape, size and position; and it is also associated with a distinct ‘ball’ on the sole, which is never present in apes. The sole of the foot is proportionately shorter than in the Laetoli prints, but it has the same general form. They were made on a sandy seashore, possibly a small river delta, whereas the Laetoli tracks were made in volcanic ash. In a word, the shape of the Trachilos prints indicate clearly that they belong to an early hominin, somewhat more primitive than the Laetoli trackmaker.
At approximately 5.7 million years, they are younger than the oldest known fossil hominin, Sahelanthropus from Chad, and contemporary with Orrorin from Kenya, but more than a million years older than Ardipithecus ramidus with its ape-like feet. This conflicts the hypothesis that Ardipithecus is a direct ancestor of later hominins. Additionally, (until this year), all fossil hominins older than 1.8 million years (the age of early Homo fossils from Georgia) came from Africa, leading most researchers to conclude that this was where the group evolved.
However, the Trachilos footprints are securely dated using a combination of foraminifera (marine microfossils) from over- and underlying beds, plus the fact that they lie just below a very distinctive sedimentary rock formed when the Mediterranean sea briefly dried out, 5.6 millon years ago. By curious coincidence, earlier this year, another group of researchers reinterpreted the fragmentary 7.2 million year old primate Graecopithecus from Greece and Bulgaria as a hominin. Graecopithecus is only known from teeth and jaws.
During the time when the Trachilos footprints were made, (a period known as the late Miocene), the Sahara Desert did not exist; savannah-like environments extended from North Africa up around the eastern Mediterranean instead. Furthermore, we know that Crete had not yet detached from the Greek mainland. It is thus not difficult to see how early hominins could have ranged across south-east Europe and well as Africa, and left their footprints on a Mediterranean shore that would one day form part of the island of Crete.
‘This discovery challenges the established narrative of early human evolution head-on and is likely to generate a lot of debate. Whether the human origins research community will accept fossil footprints as conclusive evidence of the presence of hominins in the Miocene of Crete remains to be seen,’ says Per Ahlberg.